DNS failover

Failover is a prin­ci­ple of auto­mat­ic switchover to a back­up ser­vice when the main ser­vice is no longer avail­able.

Applied to the DNS, the Failover ser­vice con­sists of mon­i­tor­ing DNS Resources Records and switch­ing to a back­up record if the main record is no longer avail­able. Dur­ing the switch, the main record con­tin­ues to be mon­i­tored and when it is avail­able again, a switch back to nor­mal is oper­at­ed.

Sur­veil­lance is car­ried out by a set of probes dis­trib­uted over dif­fer­ent net­works and world­wide geo­graph­i­cal loca­tions. The failover rules are defined upfront, whether it is a num­ber of iter­a­tions or a peri­od of time between avail­abil­i­ty checks.

The cus­tomer is informed of the changeover by an email alert, he is also informed of the return to nor­mal.